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Can the future shape the past?

Denyse O'Leary
September 17, 2016
Cosmology, News, Physics
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From Huw Price and Ken Wharton at Aeon:

Over the past forty years, a lot of ingenuity has gone into designing experiments to test the quantum predictions on which Bell’s result depends. Quantum mechanics has passed them all with flying colours. Just last year, three new experiments claimed to close almost all the remaining loopholes. ‘The most rigorous test of quantum theory ever carried out has confirmed that the “spooky action-at-a-distance” that [Einstein] famously hated… is an inherent part of the quantum world,’ as Nature put it.

Our authors propose another solution: Retrcausality, or the present an future can shape the past:

Some readers may raise a more global objection to retrocausality. Ordinarily, we think that the past is fixed while the future is open, or partly so. Doesn’t our freedom to affect the future depend on this openness? How could we affect what was already fixed? These are deep philosophical waters, but we don’t have to paddle out very far to see that we have some options. We can say that, according to the retrocausal proposal, quantum theory shows that the division between what is fixed and what is open doesn’t line up neatly with the distinction between past and future. Some of the past turns out to be open, too, in whatever sense the future is open.

To understand what sense that is, we’d need to swim out a lot further. Is the openness ‘out there in the world’, or is it a matter of our own viewpoint as agents, making up our minds how to act? Fortunately, we don’t really need an answer: whatever works for the future will work for the past, too. Either way, the result will be that our naive picture of time needs to be revised in the light of a new understanding of physics – a surprising conclusion, perhaps, but hardly a revolutionary one, more than a century after special relativity wrought its own changes on our understanding of space and time. More.

Most likely the whole system of causation would collapse under the weight of constant revisions.

See also: Economist: Can time go backward?

Is time an elemental part of nature?

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Comments
AS TO:
it is easy to read Bell’s Theorem as an argument for retrocausality. The argument shows that quantum mechanics implies that the alternative to retrocausality is action-at-a-distance. But ‘that would be magic’, as Schrödinger put it, and it conflicts with special relativity. So retrocausality it should be. At this point, some readers may feel that, while action-at-a-distance is peculiar, it’s not half as odd as the present affecting the past.
of related interest is this article defending causality, and free will, within quantum mechanics:
Accommodating Retrocausality with Free Will - 2016 Retrocausal models of quantum mechanics add further weight to the conflict between causality and the possible existence of free will. We analyze a simple closed causal loop ensuing from the interaction between two systems with opposing thermodynamic time arrows, such that each system can forecast future events for the other. The loop is avoided by the fact that the choice to abort an event thus forecasted leads to the destruction of the forecaster’s past. Physical law therefore enables prophecy of future events only as long as this prophecy is not revealed to a free agent who can otherwise render it false. This resolution is demonstrated on an earlier finding derived from the two-state vector formalism, where a weak measurement’s outcome anticipates a future choice, yet this anticipation becomes apparent only after the choice has been actually made. To quantify this assertion, weak information is described in terms of Fisher information. We conclude that an already existing future does not exclude free will nor invoke causal paradoxes. On the quantum level, particles can be thought of as weakly interacting according to their past and future states, but causality remains intact as long as the future is masked by quantum indeterminism. Quanta 2016; 5: 53–60. Conclusions We examined the possibility of free will in a retrocausal theory. Closed causal loops, which arise due to the interaction between two systems with opposing time arrows were discussed. The suggested resolution of the ensuing paradoxes relies on the thermodynamic instability of the past. Moving to the quantum realm, a similar paradox can be solved via the quantum indeterminism, which is understood to protect free will. This resonates with previous findings of Georgiev [7]. Furthermore, we discussed the strength of information transmission, where the terms strong and weak are related to strong (projective) and weak values, respectively. When information about a future event is buried under quantum indeterminism it cannot violate free will. Similarly, encrypted information, such as the one available through weak measurements, does not violate causality. The existence of free will in these time symmetric models was conjectured to resonate with a dynamical notion of time. http://quanta.ws/ojs/index.php/quanta/article/view/44
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